Mamukelashvili, a 6-foot-11 forward and a facilitator who averaged 12.3 points and 5.3 rebounds a game entering play, went down hard with 15:14 to go in the first half and didn't return.
Coach Kevin Willard said after the game that it was too soon to know how long Mamukelashvili might be out.
"I don't know for sure. It's definitely broken. But we ... have to go get an MRI [on Monday] and let our doctors and radiologists read it,'' Willard said. "There's definitely a break in there, it's just that we don't know where it is.''
On losing Mamukelashvili, Willard said that "it changes things a lot. But the good thing is, we have some guys that need to get comfortable in that role and step up in that role. ... We're going to need everyone to step up.''
Seton Hall (6-3) next plays at Rutgers on Saturday.
The Associated Press contributed to this report.